These gender differences in ratings identify real problems. First, movie ratings are overwhelmingly male, and the more popular a movie is with women, the further male ratings seem to drag the films overall rating down. A public IMDB score can influence an individuals decision to watch a movie or not, and a rating can help build public perception on the film. And yet the ratings we both see and base decisions on don't accurately represent the population's views. As Meryl Streep noted: "[Men and women] like different things. Sometimes they like the same things, but their tastes diverge. If the Tomatometer is slided so completely to one set of tastes, that drives box office in the U.S., absolutely.” Variety noted that lack of diversity in user and professional critic reviews mirror lack of diversity in the film industry overall. They also noted that there's no evidence that men like movies more than woman, or that men enjoy critiquing things more than women, but the lack of female leadership across the industry has helped exacerbate this problem. IMDB has attempted to overcome some of this affect by using a weighted average to calculate overall rating, but this is primarily to combat 'vote stuffing' by people interested in changing the rating for any reason (see, for example, The Promise), but as shown above, gender differences still have a significant effect.
Unfortunately, the movie industry still has a long way to go to achieve real diversity, and until that happens movie ratings will likely continue to reflect the industry. Movie ratings are just a symptom of a much larger problem. As consumers, we have the power to push for change with the films we choose to support financially or otherwise. So get out there, watch more movies, and check for bias in ratings before you write off a film. You'll be making a difference!